In the packaging of various goods, it is common to subject the goods sealed in the container to high temperature for various purposes. Where the container comprises a body such as glass and a cap made of plastic, it has long been known that in order to provide a durable seal, a soft elastomeric sealant should be cast in situ in the cap. One of the problems with respect to such a sealant arrangement is that the sealing material such as plastisol does not readily adhere to the plastic and therefore can slip and not stay in place.
It has heretofore been proposed, for example, in U.S. Pat. Nos. 3,603,472 and 4,244,481, that a channel be provided in the cap with annular undercut portions to retain the sealing ring which is cast in situ against axial movement, that is, from falling out of its position. However, there is still a tendency for the ring to slip or rotate.
Accordingly, among the objects of the present invention are to provide a plastic closure having a sealing ring which is cast in situ and is prevented from rotating as well as moving axially with respect to the closure.
In accordance with the invention, the closure for a container comprises a body of synthetic plastic material including a top wall and a peripheral skirt having means thereon for engaging a container. An annular channel is provided on the inner surface of the top wall at the area of juncture of the top wall and the skirt. The channel comprises integral side wall portions. At least one of said side walls comprising spaced generally vertically extending ribs and a sealing gasket is cast in situ in the channel so that the gasket interlocks with the spaced ribs.